Solid head rotary-percussion bit with rolling cutters



.J. L. KELLY, JR

SOLID HEAD ROTARY-PERGUSSION BIT WITH ROLLING GUTTERS V 2 Sheets-$heet 1Aug. 30, 1966 Filed Jan. 10 1964 JOSEPH L. KELLY, JR.

INVENTOR.

ATTORNEY Aug. 30, 1966 J. 1.. KELLY, JR 3,

SOLID HEAD ROTARY-PERCUSSION BIT WITH ROLLING CUTTERS Filed Jan. 10,1964 2 Sheets-Sheet 2 JOSEPH L. KELLY,, JR.

INVENTOR.

ATTORNEY FIGURE 4 United States Patent 3,269,46? SOLID HEADRUTARY-PERCUSSIQN BIT WITH ROLLING QUTTERS Joseph L. Kelly, .112,Houston, Tex, assignor to Hughes Tool Company, Houston, Tex, acorporation of Delaware Filed Ian. 10, 1964, Ser. No. 336,942 1 Claim.(Cl. 175336) This invention relates generally to earth boring tools andin particular to a novel drill bit that is suitable for percussiondrilling.

Prior art percussion bits can be classified into two categories: (1) thechisel type, and (2) the rolling cutter type.

The chisel type is the more prevalent of the two, its popularity beingbased primarily on its rugged construction, which is strikingly similarto that of the common chisel. In one of its simplest forms it is asingle, massive piece of metal with wedged-shaped pieces of tungstencarbide secured to its lower end. There are usually modifications suchas connecting means at its upper end and provisions for blasting thebottom of the hole with air. Basically, however, it is nothing more thana large chisel.

The disadvantage of the chisel type bit is its inability to hold gage,that is, it wears rapidly at its outer cutting surface. As aconsequence, the diameter of the bit and the hole decrease as drillingprogresses. This is permissible in mining operations such as blast holedrilling where the hole size is not particularly critical. In drillingoil and gas wells, however, the hole size must be approximately uniformso that casing of a selected size may be inserted and secured in thehole. Therefore, the chisel type bit is unsuitable for such drillingoperations.

The second category of percussion bits, the rolling cutter type, isdistinguished by the ability to hold gage. These bits are usuallysimilar to the one described in the US, patent issued to Morlan et al.,No. 2,687,875. Wear is distributed over the large, rotating surfaces ofthe cutters, a feature that increases their life at all points,including the gage surfaces. These bits were initially developed fordrilling under a static load and have proved outstanding for thatapplication. Unfor tunately, they do not have the rugged constructionthat characterizes the chisel type bit, a feature that is needed towithstand repeated impact loads. For example, the head sections, whichsupport the bearing spindles on which the cutters are mounted, areusually welded together and these welds crack easily under the highlevel cyclic loads of percussion drilling. Attempts have been made toadapt this bit type to percussion drilling by correcting this and otherweaknesses, but success has been limited.

The object of this invention is to combine the advantages of the chiseltype bit and the rolling cutter bit. The invention consists of a solid,rugged bit body (similar to the chisel type bit) equipped with rollingcutters assembled in a unique manner so as to withstand the large,fluctuating loads of percussion drilling.

This and other objects will become apparent hereinafter and in thedrawings in which:

FIGURE 1 is a perspective view showing the invention in its assembledform.

FIGURE l-A illustrates in fragmentary perspective an alternate form ofcutting structure on the bit body.

FIGURE 2 is a side elevational view of the bit body showing in detailits construction.

FIGURE 3 is a sectional view of the bit body taken as indicated by thelines and arrows 33 of FIGURE 2,

Patented August 30, 1.966

with the addition of the assembled cutters, the ring and a drill stringmember.

FIGURE 3-A is a fragmentary section showing an alternate bearingconfiguration.

FIGURE 3-B is a fragmentary section showing another alternate bearingconfiguration and also an alternate type of cutting structure on thecutters.

FIGURE 4 is a perspective view, partially in section, showing thepreferred configuration of the cutter retaining ring.

In describing the preferred embodiment of the invention, specificterminology is used to add clarity. The invention is not limited,however, by this specific terminology to the particular structuredescribed, but encompasses all equivalent structures that function in asimilar manner to accomplish a similar result.

Referring now to FIGURE 1 to give a broad description of the invention,the numeral 10 designates the body portion of the drill bit with cuttingelements 11 formed on its lower end and connecting means 12 formed onits upper end. (Splined connectors are also common in percussiondrilling but are not illustrated; any prior art connecting means may beused with the invention.) At least one but preferably a plurality ofcutters 16 are mounted on hearing spindles 22, which protrude outwardlyand upwardly in cantilever fashion (shown in FIGURES 2 and 3 but notvisible in FIGURE 1), and are formed integrally with the lower portionof body 10. A ring 14- having downwardly protruding skirts 15 is securedto the body 10. The skirts 15 retain the cutters 13 on the bearingspindles 22, providing a simply constructed and strong structure thateliminates the need for welds.

FIGURE 1 and the broad description above disclose the basic concept ofthe invention and its salient features, but do not reveal the structuraldetails that contribute so much to its strength. The concept of a cutterretainer which consists of :a ring with protruding skirts permits, forexample, the use of a unitizied bit body 10 that is made of a single,strong and massive piece of material.

The strong construction of the bit body is shown in FIGURES 2 and 3,where the numeral 16 represents a cylindrical surface on body 10 thatconfronts a matching surface 17 (see FIGURE 4) on the inside of ring 14.A radially extending surface or shelf 18 intersects the cylindricalsurface 16 to provide a positioning stop for the lower surface 30 ofring 14 that butts against shelf 18. Extending downwardly from shelf 18is a conical surface 19 that intersects a lower conical surface 35. Theconical shape of these surfaces is not essential but is merely aconvenient Way to there the body metal outwardly and downwardly toprovide strong support for cutting elements 11 and 2 7. Furthermore, theshape of these surfaces is beneficial in providing additional space forthe flushing fluid and cuttings as they move from the bore hole bottomupwardly along the exterior of the drill bit.

A flat and vertical surface 34 joins cylindrical surface 16 in such amanner that both surfaces appear as a line in FIGURE 3. Flat surface 34is required in this embodiment to provide clearance for the passage ofskirts 15 by the bit body 10 during assembly. Obviously, if conicalsurface 19 were to extend uninterrupted around the bit body, the skirts15 could not reach their final, intended position.

Cavities 21, defined by cylindrical surface 36 on one side and bearingspindle 22 on the other, are formed on opposite sides of the bit bodyIll, providing space for cutters 13. A thrust surface 32 that matches anopposed surface on each cutter 13 is also formed on the body 10,preferably having a deposit 37 of suitable hearing metal. In addition,bearing metal of a similar nature is deposited in suit-able slots 38 onthe surface of bearing spindle 22;.

Below the bearing spindles 22 is a substantially l'lOi'lzontal surfacein which are inserted a multiplicity of wear resistant insert-s 11selected from the sintered metal carbides, preferably tungsten carbide.These inserts are spaced at different radial distances from the drillaxis of rotation 26 except near the outer periphery of the bit where aplurality of outermost or heel inserts 27 are disposed to rotate at thecorner of the bore hole. Experience has shown that large amounts ofenergy are expended in drilling the corner of a bore hole; thus, moreinserts are required at that location.

The inserts 11 and 27 are preferably elongated and cylindrical, and aresecured by well known means such as by interference fit or by one of thebrazing techniques. The heel inserts 27 are angularly disposed so thattheir buried ends lie within the bit body conical surface 35. The innerinserts 11 are preferably aligned with their longitudinal axis parallelwith the bit axis 26 so that the forces transferred through them arecompressive and pass directly to the bottom of the drilled hole. Lands42 are sometimes used (they are necessary only in rare instances) togive additional support to the inserts to prevent breakage.

Cutters 13 are mounted so that they cooperate with heel inserts 27 todisintegrate the corner of the bore hole. This feature is beneficial inprotecting the heel inserts 27 from excessive wear. Furthermore, theheel inserts break up any rock teeth that tend to form on the bore holebottom, thus keeping the cones from tracking, a condition that slows thepenetration rate of the bit. The tracking problem arises when the crests39 on the teeth of each cutter fall in the indentations made on the borehole bottom by the crests of other teeth. The indentations continue togrow deeper while the ridges between them grow higher. As the crests 39of the teeth slide down these ridges, the teeth are worn by theabrasives in the earths formations. The heel inserts 27, by cooperatingwith the teeth of the cutters 13 and destroying the ridges as they form,tend to eliminate the tracking problem.

The cutters 13 have webs 4t that connect the crest 39 of the teeth attheir outer ends. This provides a large surface that may be covered withwear resistant material, such as tungsten carbide in a suitable binder,to prevent the cutters from wearing too quickly. It is usually best toprovide relief slots 41 that permit cuttings to move away from the wallof the hole and also make a milling cutter of the outer portions of thecutters.

Very few inserts 11 are required at the inner portions of the bit andthey are disposed in body It) in almost a straight row. Obviously,excessive amounts of metal are undesirable on the bottom of the bitbecause room must be provided for the escape of cuttings from the borehole bottom. For this reason the excess metal is removed by forminggrooves 28 in an oblique fashion as is shown in FIGURES 1 and 2, perhapsmore clearly in FIGURE 1.

To remove the cuttings from the bore hole bottom, a central passage 24is formed in the upper part of the bit body Iii. At least one passage 23directs the fluid to the bore hole bottom where the cuttings areentrained and removed from the hole. Preferably, a plurality ofpassageways are used, at least some of which are angularly disposed, asare the passageways of FIGURE 1. This configuration is beneficial inblasting the corner of the hole with a high velocity stream of fluidthat removes quickly the cuttings that tend to lie dormantly in thishard-to-reach area.

The interference ring 14 is illustrated in FIGURE 4 where the skirts 15are shown, including the inner surfaces 43 that abut the ends 52 ofbearing spindles 22 after assembly to retain cutters 13. The cylindricalsurface 17 of the ring is a few thousandths of an inch smaller indiameter (.003 inch interference on a cylindrical surface of 3 /8diameter for a 6% inch diameter bit was found suitable) than thematching cylindrical surface 16 of the bit body 10. To prevent the ring14 from rotating with respect to the bit body 1% during assembly, it ispreferable to have guide means such as key seat 44 that confronts amatching protrusion on the bit body (not shown). The inner surface 43 ofring 15 has a groove 45 filled with a good bearing metal such as silver,silver alloy, iron or cobalt based alloy. The cutters 13 are generallypushed inwardly at the gage of the hole during drilling and this cocksthem so that they contact deposit 37 on surface 32 of the bit body 10and groove 45 of ring 14.

In View of the detailed description above, the numerous advantages ofthe invention should be apparent, espe' cially its simple and ruggedconstruction. The unitized bit body 10, for example, is fabricated ofonly one massive piece of metal that offers durability to the bit. Thecutters, secured to the body by novel means, provides resistance to gagewear. The novel retaining means eliminates the need for welds. Thus theinvention combines the advantages of prior art bits and provides a longneeded advance in the drilling art.

Various modifications to the structure will occur to those of averageskill in the art, but particularly noteworthy is the fact that theinvention is not limited to the cutting elements 11 and 27 shown inFIGURE 1. FIG- URE LA, for example, illustrates a modification havingchisel-like cutting elements 46 that are well known in the art. This andother old art cutting structures are within the scope of the inventionsince the inventive concept encompasses a novel body construction andcone retaining means and is not limited to the cutting structures shownand described.

Although the bearings of spindles 22 and cutters 13 are preferably ofthe journal type as is shown in FIGURE 3, the invention is not limitedto journal bearings, but encompasses all old art devices such as theroller bearing of FIGURE 3-A. Here the spindle is designated by numeral47, which has an annular groove 48 into which are inserted rollers 49.Rolling cutter 50 is inserted over the rollers 49 and the interferencering is assembled so that skirt 51 confronts the end of spindle 47 toretain cutter 50 thereon. This construction is not preferred, however,since the rollers 49 absorb energy during impact loading, therebydecreasing the efficiency of the bit.

FIGURE 3B is similar to FIGURE 3A in that it illustrates ananti-friction bearing consisting of balls 53 mounted in matchingraceways in bearing spindle 47 and cutter 54. Journal surface 55 incutter 54 and surface 62 on bearing spindle 47 constitute a journalbearing that cooperates with the anti-friction bearing to support thevarious forces. In this embodiment cutter 54 is assembled on bearingspindle 47, and then the balls 53 are inserted through drilled hole 63in bearing spindle 47. Then a plug 56 is inserted into drilled hole 63and the skirt 51 of the interference ring is assembled, retaining theplug 56 which in turn retains the balls 53 in their raceways. In thisembodiment the advantages of eliminating welds is achieved by the use ofa ring with protruding skirts 51, and is thus within the inventiveconcept.

In view of the bearing modifications illustrated in FIG- URES 3-A and3-B, it is apparent that many old art hearing structures are operablewith the invention. Hence, the invention is not limited to themodifications illustrated; rather, the wide range of the applicabilityof the invention is shown thereby.

Another modification of the invention is illustrated in FIGURE 3-B Wherethe cutter 54 is illustrated as having a plurality of wear resistantinserts 57. These inserts are generally cylindrical in cross-section andare secured by interference fit in matching, cylindrical holes in thecutter 54.

One criterion for the selection of cutters is the type formation to bedrilled. Wear of the cutters l3 and inaaeaseo serts 11 and 27 of bodyIt) should be balanced and this depends to a large extent on theformations drilled. Tests on various granites, for examples, indicatedthat wear is better balanced by using milled cutters l3 and cylindricalinserts with blunt, protruding ends in the bit body it). When cutterswith inserts, such as cutter 54 of FIGURE 3-B, were used, the cutterslasted much longer than the 5 cutting elements of the bit body. It isbetter design practice to balance the wear between the various parts andfor this reason the milled cutters are preferred. It may proveeconomically feasible, however, to disassemble the bit on the drillinglocation and assemble the partially worn cutters on new bit bodies. Ifso, the inserts cutters 54 of FIGURE 3-B may prove to be the better ofthe two type illustrated.

The number of bearing spindles and cutters and their location withrespect to the rest of the drill is not especially critical as far asthe basic concept is concerned. Cutters 13 may be moved upwardly fromthe location shown in FIGURE 1 so that they merely ream the hole.Conversely, they can be moved downwardly so that cutter crests 39 andwebs 40 cut a kerf on the bore hole bottom. In the latter arrangementthe body inserts 11 cut only the resulting core, and heel inserts 27 maybe eliminated.

As is clearly illustrated, it is preferable to have at least twocutters, although one cutter may be used. When using two oppositelylocated cutters, the bit will rotate more consistently aboutlongitudinal axis 26, whereas the use of only one cutter frequentlycauses the bit to rotate about an axis other than axis 26. The use ofmore than two cutters produces results in this regard similar to the useof two cutters, and the decision to illustrate a two cutter design isprompted merely by the resulting simplification of construction.

The bearing spindles 22 have been described as being integral with bitbody and this is indeed the preferred arrangement. Nevertheless, thespindles 22 can be made separately and inserted into the bit body 10 byinterference fit or by other suitable means. Although this arrangementis undoubtedly weaker than the integral structure, the advantage ofusing the ring as a cutter retainer still obtains and thus thismodification is within the inventive concept.

Ring 14 is preferably an interference ring, which encompasses ringssecured to the bit body by such old art methods of assembly as theshrink fit and the press fit. On the other hand the ring 14- may beretained by the drill string member 58 of FIGURE 3. In this embodimentthe shoulder 59 of the drill collar 58 engages shoulders 6t) and 61 ofring 14 and bit body 10 during assembly and thereafter ring 14 cannot beremoved without removing the drill collar.

iii

The bit body ill of FIGURE 1 has been described as being flat orhorizontal across its lower surface 20. The invention, however, is notlimited to such constructions but encompasses rounded, concave, convexor stepped surfaces. The flat configuration is thought best, however,and for that reason is illustrated in the drawing.

Considerable geometrical details have been recited in describing thepreferred embodiment, especially in relation to the bit body 1d. Thesedetails should not be taken as limitating the invention, for there areperhaps infinite geometrical variations that are possible. These detailsare given to enable those in the art to understand how the invention ispreferably made.

The invention has been described as one especially suitable forpercussion drilling. Testing has in fact been restricted to percussiondrilling because this is where most fatigue problems reside at present.The invention nevertheless has utility as a drill bit suitable forconventional, rotary drilling. There are numerous drill bits that have abody portion and rolling cutters. None of them, how ever, have the novelstructure of the present invention.

I claim:

In a rotary-percussion bit of the type having a solid massive body withan upper end adapted to be connected to a drill string member and alower end extending diametrically substantially the full width of aborehole to be cut, there being fixed percussive cutting elementssecured in and protruding downwardly from said lower end and disposed tocut a full borehole While the bit is rotated and subject to percussionduring drilling, the improvement comprising at least one bearing spindlesecured to said bit body and extending upwardly and outwardly therefromwith its outer end terminating unsecured in cantilever fashion, arolling cutter rotatably mounted on said bearing spindle, said cutterbeing disposed to assist said percussive cutting elements. In cuttingthe outer portion of the borehole formed by said elements duringdrilling, and a ring member secured to the bit body above said bearingspindle, said ring having a downwardly extending skirt which confrontsthe unsupported end of the bearing spindle to retain the cutter thereon.

References Cited by the Examiner UNITED STATES PATENTS 1,816,568 7/1931Carlson l336 2,166,462 7/1939 Catland l75333 2,320,136 5/1943 Kammerer-333 2,851,253 9/1958 Boice 175-355 JACOB L. NACKENOFF, PrimaryExaminer.

CHARLES E. OCONNELL, Examiner.

N. C. BYERS, Assistant Examiner.

